As an apparatus for processing a substrate such as a semiconductor wafer (hereinafter, referred to as a “wafer”) in a manufacturing process of a semiconductor device, there is a plasma etching device which etches a wafer by irradiating plasma onto the wafer.
In a plasma etching process, an etching gas including fluorine, chlorine, and oxygen is activated by a radio frequency electric field to generate plasma. The plasma includes active species such as charged particles (hereinafter, referred to as “ions”) and neutral particles (hereinafter, referred to as “radicals”). The active species such as ions or radials react with a wafer surface to generate a reaction product and the generated reaction product is volatilized so that the etching process is performed.
Recently, in the manufacturing process of a semiconductor device, since a diameter of a wafer is increased, it becomes difficult to uniformize an etching speed in a wafer plane. Therefore, in order to improve in-plane uniformity, it has been attempted to uniformize a density of the active species in a center area and a peripheral area in the wafer plane by adjusting the amount of an etching gas supplied from an upper electrode (See, e.g., Patent Document 1).